There is a growing desire in many workplace and other environments to separate the display of a computer system from the application processing parts. In the desired configuration, the display is physically located at the user's desktop, while the processing components of the computer are placed in a central location. The display is then connected to the data processor with some method of communication such as a computer network.
Various methods have been proposed to transfer display content across a network, including transferring graphic commands or encoded pixel maps representing the display image. These methods are acceptable for the transfer of less dynamic content such as text, background and pictures but are poorly suited to the transfer of dynamic video inserts. Video is usually not rendered using graphics commands so such commands aren't available for transfer. The transfer of compressed video would place a burden of full-featured decoding application software and hardware at the remote display and pixel transfer methods would easily saturate a corporate network unless the content was re-compressed.
Optimized methods for transferring areas of rapidly changing image content surrounded by other areas with different image types such as a video insert surrounded by pictures and text have not been addressed by prior art. Video content poses a unique problem in that it generates too much data for raw transfer across a network, is unsuitable for static image compression methods such as JPEG2000 and conventional video encoders such as H.264 or MPEG-4 FGS are complex, intrusive and inefficient to implement, especially considering the infrequent requirement for such encoding in many computing environments. Moreover, a video clip on a computer display is usually derived from a compressed source such as a DVD or broadcast network. A second video encoding phase adds unwanted latency and further reduces image quality. Additionally a standard encoded video stream would mandate a video decoder at the display system which is in conflict with cost and maintenance objectives associated with remote display systems.
Hybrid methods such as MJPEG developed to improve random access are capable of transmitting a series of independent JPEG images without applying inter-frame prediction methods. These methods offer limited compression and tend to consume high network bandwidth in applications such as standard video operating at high frame rates. Therefore they remain best suited to specialized applications like broadcast resolution video editing or surveillance systems where the frame rate is low. One variation on MJPEG uses differential encoding so that only changed DCT coefficients are encoded. However, in a video application, much of the content changes on every frame rendering this method ineffective.
In summary, existing methods developed specifically to transfer computer display images are not effective methods for transferring video. Still image and video compression techniques lack the necessary compression capabilities, require intrusive components or increased complexity. This results in higher equipment and maintenance costs and lower performance. Therefore, it is desirable to innovate new methods for transferring video sequences across computer networks to remote display systems.